[PATCH 0/2] genirq and Hyper-V: Clean up handling of add_interrupt_randomness()

[PATCH 0/2] genirq and Hyper-V: Clean up handling of add_interrupt_randomness()

[Michael Kelley]

From: Michael Kelley <mhklinux@outlook.com>

The Hyper-V ISRs are calling add_interrupt_randomness() as a
primary source of entropy in VMs, since the VMs don't have another
good source. The call is currently in the ISRs as a common place to
handle both x86/x64 and arm64. On x86/x64, hypervisor interrupts come
through a custom sysvec entry, and on arm64 they come through an
emulated GICv3. GICv3 uses the generic handler handle_percpu_devid_irq(),
which does not do add_interrupt_randomness(), unlike its counterpart
handle_percpu_irq().

Cleanup this somewhat confusing situation by doing the
add_interrupt_randomness() in handle_percpu_devid_irq(), and remove
it from the Hyper-V ISRs. Then only the Hyper-V custom sysvec path,
which plays the role of a generic interrupt handler, needs to do
add_interrupt_randomness(). As a result of this change, no
device drivers are calling add_interrupt_randomness(), which is
appropriate.

The change is broken into two patches since it spans generic
interrupt handling code and Hyper-V specific code. But the two
patches should be taken together through the same tree. It's
OK to have a bisect window where add_interrupt_randomness() is
done in both places, but taking the Hyper-V patch first could leave
a bisect window where add_interrupt_randomness() is not done in
either place.

Michael Kelley (2):
  genirq/chip: Do add_interrupt_randomness() in
    handle_percpu_devid_irq()
  Drivers: hv: Move add_interrupt_randomness() to hypervisor callback
    sysvec

 arch/x86/kernel/cpu/mshyperv.c | 2 ++
 drivers/hv/mshv_synic.c        | 3 ---
 drivers/hv/vmbus_drv.c         | 3 ---
 kernel/irq/chip.c              | 3 +++
 4 files changed, 5 insertions(+), 6 deletions(-)

-- 
2.25.1

[PATCH 1/2] genirq/chip: Do add_interrupt_randomness() in handle_percpu_devid_irq()

[Michael Kelley]

From: Michael Kelley <mhklinux@outlook.com>

handle_percpu_devid_irq() is a version of handle_percpu_irq() but with
the addition of a pointer to a per-cpu devid. However, handle_percpu_irq()
does add_interrupt_randomness(), while handle_percpu_devid_irq() currently
does not. Add the missing add_interrupt_randomness(), as it is needed
when per-cpu interrupts with devid's are used in VMs for interrupts
from the hypervisor.

Signed-off-by: Michael Kelley <mhklinux@outlook.com>
---
 kernel/irq/chip.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
index 6147a07d0127..6c9b1dc4e7d4 100644
--- a/kernel/irq/chip.c
+++ b/kernel/irq/chip.c
@@ -14,6 +14,7 @@
 #include <linux/interrupt.h>
 #include <linux/kernel_stat.h>
 #include <linux/irqdomain.h>
+#include <linux/random.h>
 
 #include <trace/events/irq.h>
 
@@ -929,6 +930,8 @@ void handle_percpu_devid_irq(struct irq_desc *desc)
 			    enabled ? " and unmasked" : "", irq, cpu);
 	}
 
+	add_interrupt_randomness(irq);
+
 	if (chip->irq_eoi)
 		chip->irq_eoi(&desc->irq_data);
 }
-- 
2.25.1

[PATCH 2/2] Drivers: hv: Move add_interrupt_randomness() to hypervisor callback sysvec

[Michael Kelley]

From: Michael Kelley <mhklinux@outlook.com>

The Hyper-V ISRs, for normal guests and when running in the
hypervisor root patition, are calling add_interrupt_randomness() as a
primary source of entropy. The call is currently in the ISRs as a common
place to handle both x86/x64 and arm64. On x86/x64, hypervisor interrupts
come through a custom sysvec entry, and do not go through a generic
interrupt handler. On arm64, hypervisor interrupts come through an
emulated GICv3. GICv3 uses the generic handler handle_percpu_devid_irq(),
which does not do add_interrupt_randomness() -- unlike its counterpart
handle_percpu_irq(). But handle_percpu_devid_irq() is now updated to do
the add_interrupt_randomness(). So add_interrupt_randomness() is now
needed only in Hyper-V's x86/x64 custom sysvec path.

Move add_interrupt_randomness() from the Hyper-V ISRs into the Hyper-V
x86/x64 custom sysvec path, matching the existing STIMER0 sysvec path.
With this change, add_interrupt_randomness() is no longer called from any
device drivers, which is appropriate.

Signed-off-by: Michael Kelley <mhklinux@outlook.com>
---
 arch/x86/kernel/cpu/mshyperv.c | 2 ++
 drivers/hv/mshv_synic.c        | 3 ---
 drivers/hv/vmbus_drv.c         | 3 ---
 3 files changed, 2 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index 9befdc557d9e..a7dfc29d3470 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -161,6 +161,8 @@ DEFINE_IDTENTRY_SYSVEC(sysvec_hyperv_callback)
 	if (vmbus_handler)
 		vmbus_handler();
 
+	add_interrupt_randomness(HYPERVISOR_CALLBACK_VECTOR);
+
 	if (ms_hyperv.hints & HV_DEPRECATING_AEOI_RECOMMENDED)
 		apic_eoi();
 
diff --git a/drivers/hv/mshv_synic.c b/drivers/hv/mshv_synic.c
index 43f1bcbbf2d3..e2288a726fec 100644
--- a/drivers/hv/mshv_synic.c
+++ b/drivers/hv/mshv_synic.c
@@ -12,7 +12,6 @@
 #include <linux/mm.h>
 #include <linux/interrupt.h>
 #include <linux/io.h>
-#include <linux/random.h>
 #include <linux/cpuhotplug.h>
 #include <linux/reboot.h>
 #include <asm/mshyperv.h>
@@ -445,8 +444,6 @@ void mshv_isr(void)
 		mb();
 		if (msg->header.message_flags.msg_pending)
 			hv_set_non_nested_msr(HV_MSR_EOM, 0);
-
-		add_interrupt_randomness(mshv_sint_vector);
 	} else {
 		pr_warn_once("%s: unknown message type 0x%x\n", __func__,
 			     msg->header.message_type);
diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 1d71c28fadba..3faa74e49a6b 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -32,7 +32,6 @@
 #include <linux/ptrace.h>
 #include <linux/sysfb.h>
 #include <linux/efi.h>
-#include <linux/random.h>
 #include <linux/kernel.h>
 #include <linux/syscore_ops.h>
 #include <linux/dma-map-ops.h>
@@ -1356,8 +1355,6 @@ static void __vmbus_isr(void)
 
 	vmbus_message_sched(hv_cpu, hv_cpu->hyp_synic_message_page);
 	vmbus_message_sched(hv_cpu, hv_cpu->para_synic_message_page);
-
-	add_interrupt_randomness(vmbus_interrupt);
 }
 
 static DEFINE_PER_CPU(bool, vmbus_irq_pending);
-- 
2.25.1

Re: [PATCH 2/2] Drivers: hv: Move add_interrupt_randomness() to hypervisor callback sysvec

[Thomas Gleixner]

On Thu, Apr 02 2026 at 13:24, Michael Kelley wrote:
> From: Michael Kelley <mhklinux@outlook.com>
>
> The Hyper-V ISRs, for normal guests and when running in the
> hypervisor root patition, are calling add_interrupt_randomness() as a
> primary source of entropy. The call is currently in the ISRs as a common
> place to handle both x86/x64 and arm64. On x86/x64, hypervisor interrupts
> come through a custom sysvec entry, and do not go through a generic
> interrupt handler. On arm64, hypervisor interrupts come through an
> emulated GICv3. GICv3 uses the generic handler handle_percpu_devid_irq(),
> which does not do add_interrupt_randomness() -- unlike its counterpart
> handle_percpu_irq(). But handle_percpu_devid_irq() is now updated to do
> the add_interrupt_randomness(). So add_interrupt_randomness() is now
> needed only in Hyper-V's x86/x64 custom sysvec path.
>
> Move add_interrupt_randomness() from the Hyper-V ISRs into the Hyper-V
> x86/x64 custom sysvec path, matching the existing STIMER0 sysvec path.
> With this change, add_interrupt_randomness() is no longer called from any
> device drivers, which is appropriate.
>
> Signed-off-by: Michael Kelley <mhklinux@outlook.com>

Acked-by: Thomas Gleixner <tglx@kernel.org>

[tip: irq/core] genirq/chip: Invoke add_interrupt_randomness() in handle_percpu_devid_irq()

[tip-bot2 for Michael Kelley]

The following commit has been merged into the irq/core branch of tip:

Commit-ID:     fd7400cfcbaaa1f3d1b904711d9daf029e996364
Gitweb:        https://git.kernel.org/tip/fd7400cfcbaaa1f3d1b904711d9daf029e996364
Author:        Michael Kelley <mhklinux@outlook.com>
AuthorDate:    Thu, 02 Apr 2026 13:23:59 -07:00
Committer:     Thomas Gleixner <tglx@kernel.org>
CommitterDate: Thu, 02 Apr 2026 23:03:29 +02:00

genirq/chip: Invoke add_interrupt_randomness() in handle_percpu_devid_irq()

handle_percpu_devid_irq() is a version of handle_percpu_irq() but with the
addition of a pointer to a per-CPU devid.

However, handle_percpu_irq() invokes add_interrupt_randomness(), while
handle_percpu_devid_irq() currently does not.

Add the missing add_interrupt_randomness(), as it is needed when per-CPU
interrupts with devid's are used in VMs for interrupts from the hypervisor.

Signed-off-by: Michael Kelley <mhklinux@outlook.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260402202400.1707-2-mhklkml@zohomail.com
---
 kernel/irq/chip.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
index 6147a07..6c9b1dc 100644
--- a/kernel/irq/chip.c
+++ b/kernel/irq/chip.c
@@ -14,6 +14,7 @@
 #include <linux/interrupt.h>
 #include <linux/kernel_stat.h>
 #include <linux/irqdomain.h>
+#include <linux/random.h>
 
 #include <trace/events/irq.h>
 
@@ -929,6 +930,8 @@ void handle_percpu_devid_irq(struct irq_desc *desc)
 			    enabled ? " and unmasked" : "", irq, cpu);
 	}
 
+	add_interrupt_randomness(irq);
+
 	if (chip->irq_eoi)
 		chip->irq_eoi(&desc->irq_data);
 }

Re: [PATCH 2/2] Drivers: hv: Move add_interrupt_randomness() to hypervisor callback sysvec

[Wei Liu]

On Thu, Apr 02, 2026 at 01:24:00PM -0700, Michael Kelley wrote:
> From: Michael Kelley <mhklinux@outlook.com>
> 
> The Hyper-V ISRs, for normal guests and when running in the
> hypervisor root patition, are calling add_interrupt_randomness() as a
> primary source of entropy. The call is currently in the ISRs as a common
> place to handle both x86/x64 and arm64. On x86/x64, hypervisor interrupts
> come through a custom sysvec entry, and do not go through a generic
> interrupt handler. On arm64, hypervisor interrupts come through an
> emulated GICv3. GICv3 uses the generic handler handle_percpu_devid_irq(),
> which does not do add_interrupt_randomness() -- unlike its counterpart
> handle_percpu_irq(). But handle_percpu_devid_irq() is now updated to do
> the add_interrupt_randomness(). So add_interrupt_randomness() is now
> needed only in Hyper-V's x86/x64 custom sysvec path.
> 
> Move add_interrupt_randomness() from the Hyper-V ISRs into the Hyper-V
> x86/x64 custom sysvec path, matching the existing STIMER0 sysvec path.
> With this change, add_interrupt_randomness() is no longer called from any
> device drivers, which is appropriate.
> 
> Signed-off-by: Michael Kelley <mhklinux@outlook.com>

Acked-by: Wei Liu <wei.liu@kernel.org>

[tip: irq/core] Drivers: hv: Move add_interrupt_randomness() to hypervisor callback sysvec

[tip-bot2 for Michael Kelley]

The following commit has been merged into the irq/core branch of tip:

Commit-ID:     e8be82c2d77ec1bb0148406e54b105028a83537e
Gitweb:        https://git.kernel.org/tip/e8be82c2d77ec1bb0148406e54b105028a83537e
Author:        Michael Kelley <mhklinux@outlook.com>
AuthorDate:    Thu, 02 Apr 2026 13:24:00 -07:00
Committer:     Thomas Gleixner <tglx@kernel.org>
CommitterDate: Sat, 04 Apr 2026 21:01:56 +02:00

Drivers: hv: Move add_interrupt_randomness() to hypervisor callback sysvec

The Hyper-V ISRs, for normal guests and when running in the hypervisor root
patition, are calling add_interrupt_randomness() as a primary source of
entropy. The call is currently in the ISRs as a common place to handle both
x86/x64 and arm64.

On x86/x64, hypervisor interrupts come through a custom sysvec entry, and
do not go through a generic interrupt handler.

On arm64, hypervisor interrupts come through an emulated GICv3. GICv3 uses
the generic handler handle_percpu_devid_irq(), which does not do
add_interrupt_randomness() -- unlike its counterpart
handle_percpu_irq().

But handle_percpu_devid_irq() is now updated to do the
add_interrupt_randomness(). So add_interrupt_randomness() is now needed
only in Hyper-V's x86/x64 custom sysvec path.

Move add_interrupt_randomness() from the Hyper-V ISRs into the Hyper-V
x86/x64 custom sysvec path, matching the existing STIMER0 sysvec path.

With this change, add_interrupt_randomness() is no longer called from any
device drivers, which is appropriate.

Signed-off-by: Michael Kelley <mhklinux@outlook.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Acked-by: Wei Liu <wei.liu@kernel.org>
Link: https://patch.msgid.link/20260402202400.1707-3-mhklkml@zohomail.com
---
 arch/x86/kernel/cpu/mshyperv.c | 2 ++
 drivers/hv/mshv_synic.c        | 3 ---
 drivers/hv/vmbus_drv.c         | 3 ---
 3 files changed, 2 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index 9befdc5..a7dfc29 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -161,6 +161,8 @@ DEFINE_IDTENTRY_SYSVEC(sysvec_hyperv_callback)
 	if (vmbus_handler)
 		vmbus_handler();
 
+	add_interrupt_randomness(HYPERVISOR_CALLBACK_VECTOR);
+
 	if (ms_hyperv.hints & HV_DEPRECATING_AEOI_RECOMMENDED)
 		apic_eoi();
 
diff --git a/drivers/hv/mshv_synic.c b/drivers/hv/mshv_synic.c
index 43f1bcb..e2288a7 100644
--- a/drivers/hv/mshv_synic.c
+++ b/drivers/hv/mshv_synic.c
@@ -12,7 +12,6 @@
 #include <linux/mm.h>
 #include <linux/interrupt.h>
 #include <linux/io.h>
-#include <linux/random.h>
 #include <linux/cpuhotplug.h>
 #include <linux/reboot.h>
 #include <asm/mshyperv.h>
@@ -445,8 +444,6 @@ void mshv_isr(void)
 		mb();
 		if (msg->header.message_flags.msg_pending)
 			hv_set_non_nested_msr(HV_MSR_EOM, 0);
-
-		add_interrupt_randomness(mshv_sint_vector);
 	} else {
 		pr_warn_once("%s: unknown message type 0x%x\n", __func__,
 			     msg->header.message_type);
diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index bc4fc19..e7ac79e 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -32,7 +32,6 @@
 #include <linux/ptrace.h>
 #include <linux/sysfb.h>
 #include <linux/efi.h>
-#include <linux/random.h>
 #include <linux/kernel.h>
 #include <linux/syscore_ops.h>
 #include <linux/dma-map-ops.h>
@@ -1361,8 +1360,6 @@ static void __vmbus_isr(void)
 
 	vmbus_message_sched(hv_cpu, hv_cpu->hyp_synic_message_page);
 	vmbus_message_sched(hv_cpu, hv_cpu->para_synic_message_page);
-
-	add_interrupt_randomness(vmbus_interrupt);
 }
 
 static DEFINE_PER_CPU(bool, vmbus_irq_pending);